Allistatin is the collective name for two chemicals, allistatin I and allistatin II, which may be found in garlic. There is no conclusive evidence of its existence, or the existence of the related compound garlicin. It is a sulfur-free chemical and plays an active role within garlic. It is most likely a flavonoid.
There is no experimental evidence of the structure of allistatin; some studies claim it is similar to cyanidin, while others found it shared similarities with garlicin (but not allicin).
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